Patent Document 1 below, for example, discloses a transmission structure including a bearing for supporting a main shaft of a dog-clutch type transmission for two-wheel motorcycles.
Specifically, the disclosed structure employs a ball bearing as the bearing for supporting the main shaft. A lubricant guide member for regulating the amount of lubricant supplied in the main shaft is provided at a position axially outside of an outer race of the ball bearing. The lubricant guide member is pressed against the outer race by elastic force of an O-ring placed on the axially opposite side of the ball bearing.
Shifting or striking noises are sometimes produced during the speed change operation carried out by the dog-clutch type transmission.
In the transmission for saddle-type vehicles, a main shaft and a counter shaft are provided, and, generally, on each of these shafts are provided shifter gears that are axially shiftable, fixed gears that are axially not shiftable, and a dog clutches between the shifter and fixed gears. During the speed change operation in which the dog clutch between adjoining shifter and fixed gears is engaged, dog teeth of the dog clutch, rotating at different speeds, strike each other at their side surfaces, so that shifting or striking noises are sometimes produced. The striking noises accompanied by vibrations are produced at the striking area of the dog clutch teeth, and the vibrations are transmitted from the gear teeth of the dog clutch to the main shaft or the counter shaft, to the outer race of the ball bearing supporting the main shaft or the counter shaft, to the part of the transmission case supporting the outer race, to the transmission case, and to the transmission cover, so that striking noises are released to the outside of the transmission.
Though the Patent Document 1 below does not mention in detail, the use of the lubricant guide member pressed against the outer race of the bearing by elastic force of the O-ring is useful to some degree to reduce vibrations of the outer race, resulting from vibrations produced in the engaging area of the dog clutch teeth during the speed change operation. Therefore the use of the lubricant guide member pressed against the bearing outer race is expected to have a vibration reducing effect to a certain degree during the speed change operation.
However, the lubricant guide member pressed against the ball bearing is made of metal, so that the ball bearing and the lubricant guide member are supposed to integrally vibrate together. Therefore, the ball bearing and the lubricant guide member are considered to perform a certain vibration-preventing effect on the ball bearing and so on, but the effect is low because the volume of the O-ring cannot be enough. The same is true in case the bearing is a roller bearing and the like.
For this reason, further reduction of the striking noises in relation to the known structure is required.